Diamond may be considered to be a very unique material. It has relatively high hardness, high thermal conductivity, high electric resistivity, a low coefficient of friction and is substantially inert to attacks from most chemicals. For tribological applications, diamond may be considered an excellent material to inhibit erosion, abrasion and sliding wear.
Natural diamond may be considered too expensive and too small in size to protect industrial component surfaces. Similarly, synthetic diamond, which may be used in polishing, grinding and cutting, particularly in machining, mining or oil/natural gas exploration applications, may be difficult to use as a protective coating on components to inhibit erosion, abrasion, wear and corrosion.
It may be possible to form diamond coatings on larger surface areas using a few methods including hot filament chemical vapor deposition (HFCVD) and microwave plasma enhanced chemical vapor deposition (MPECVD). However, such are understood to require high temperature and a limited range of substrate materials. For example, diamond may be deposited on tungsten carbide (WC) for cutting applications. However, due to crystallinity, the coating surface may be quite rough. Consequently, with the exception of cutting applications, diamond coatings may be understood to rarely be used on substrates comprising, for example, steel, titanium (Ti) alloys and aluminum (Al) alloys, as well as substrates for tribological applications.
A coating which may be used as an alternative to diamond is a coating of diamond-like carbon (DLC). A diamond-like carbon coating may be understood herein to be a carbon coating with the amorphous structure, generally containing a high concentration of hydrogen. DLC coatings may be understood to have reasonable hardness, good wear resistance, a relatively low coefficient of friction and are chemically inert. Unlike diamond coatings, however, DLC coatings may be deposited on substrates including steel, titanium (Ti) alloys and aluminum (Al) alloys using a bonding layer, typically of silicon (Si) or silicon carbide (SiC). Silicon may be understood to bond with DLC due to a formation of a thin layer of silicon carbide at the interface between the silicon and DLC.
However, DLC coatings are understood to be useful only to about 400° C., above which temperature graphitization of the carbon may occur. Furthermore, DLC coatings may be understood to be relatively brittle or of low toughness. As a result, DLC coatings are commonly used for low stress sliding wear applications, but not for severe environments including erosion or abrasion under high stress or heavy load.
In light of the foregoing deficiencies, what is needed a coating containing diamond which may offer increased performance, such as use temperature, hardness and toughness, as compared to existing hard coatings. Such coatings may then be applied using manufacturing processes for existing hard coatings and would be applicable to a wide range of substrate materials.